OLYMPIA, Wash. (AP) — Authorities have been investigating the disappearance of Susan Powell as a murder for at least several months, while they publicly left open the possibility that the Utah mother might be found alive.
A search warrant obtained by The Associated Press through a public records request Tuesday showed that police were investigating three felonies in Utah: first-degree murder, kidnapping and obstructing a public servant.
Salt Lake County District Attorney Sim Gill acknowledged for the first time that they believe Powell is dead, saying in an AP interview that the case is being handled as a murder investigation.
WATCH ABOVE: Social Worker Tells 911 That The Powell Home 'Exploded
Gill wouldn't discuss the evidence, but said authorities don't have enough information to file charges in the case.
"I think when I talk about it as a missing persons case, that's because we haven't located the body of Susan Powell," Gill said. "Do we think that she may have met harm? Sure.
"I think that's been an ongoing assumption with law enforcement," he said, adding that the case remains "open and active."
Investigators are now reassessing the case after her husband and "person of interest" in her 2009 disappearance, Josh Powell, torched his home this weekend, killing himself and their two young children.
PHOTOS: (Story Continues Below)
Pierce County sheriff's deputies and Graham firefighters work through the wreckage of a home in Graham, Wash. where the bodies of Josh Powell and his two sons were found on Feb. 5, 2012 in a double-homicide suicide. The boys had just been brought by a Child Protective Services worker to Powell's home for a supervised visit when police say the dad deliberately blew up the house. A judge had denied the previous week a request by Powell to regain custody of his sons, who had been living with the parents of his missing wife, Susan.
Pierce County sheriff's officials said it appears Josh Powell used an accelerant to increase the power of a gas fire that he intentionally set to kill himself and his two sons inside his Graham, Wash., home on Feb. 5, 2012. The saga of the Powell family began in 2009 when Josh Powell reported that his wife, Susan, had gone missing. That night he claimed he took his sons on an overnight camping trip in freezing temperatures.
The explosion at Josh Powell's home left smoldering remains in Graham, Wash. Police say Powell deliberately detonated the home moments after a Child Protective Services worker brought his sons Braden, 5, and Charles, 7, for a supervised visit.
This undated photo provided by Chuck and Judy Cox shows their grandsons Braden, left, and Charlie Powell. (AP Photo/Courtesy Chuck and Judy Cox)
This undated photo provided by Chuck and Judy Cox shows them with their grandsons, Charlie, left, and Braden, right. Charlie and Braden were killed along with their father, Josh Powell, on Sunday in what police said was an intentional fire set by Powell. The Coxes are the parents of Powell's wife, Susan, who has been missing since 2009. (AP Photo/Courtesy Chuck and Judy Cox)
This undated photo provided by Chuck and Judy Cox shows Braden, left, and Charlie Powell. (AP Photo/Courtesy Chuck and Judy Cox)
Police and other officials from Washington state and Utah view charred rubble, Monday, Feb. 6, 2012, at of the home where Josh Powell and his two sons were killed in the fire Powell set Sunday. (AP Photo/Ted S. Warren)
In this pool photo provided by the Pierce County Sheriff's Dept., a melted gas can is marked with an evidence flag, Monday, Feb. 6, 2012, in the rubble of the home in Graham, Wash., where Josh Powell and his two sons were killed. (AP Photo/Pierce County Sheriff's Dept., Ed Troyer, Pool)
This image from Friends and Family of Susan Cox Powell Facebook page shows missing Utah mother Susan Cox Powell. Powell has been missing since December 6, 2009. Her husband Josh Powell was a person of interest in her disappearance before he killed himself and their two sons on Feb. 5, 2012.
Chuck and Judy Cox, the parents of missing Utah mother Susan Cox, talk to reporters at their home in Puyallup, Wash., Monday, Feb. 6, 2012. They had custody of their grandchildren, Charlie and Braden Powell, who were killed by their father Josh Powell during a supervised visit to his house on Sunday. Their daughter Susan Cox Powell went missing in December 2009 from the West Valley City, Utah home where she lived with her husband and sons. (AP Photo/Ted S. Warren)
Supporters held an impromptu candlelight vigil for Braden and Charlie Powell, who were killed by their father Josh when he deliberately torched his Graham, Wash. home on Feb. 5, 2012. The brothers had been living with their maternal grandparents in a simmering custody dispute stemming from their mother's disappearance in Utah in 2009.
Flowers and two stuffed animals are left near crime-scene tape, Monday, Feb. 6, 2012, near the home where Josh Powell and his two sons were killed Sunday, in Graham, Wash., in what police said appeared to be a deliberately set fire. Powell's wife Susan went mysteriously missing from their West Valley City, Utah, home in December 2009. (AP Photo/Ted S. Warren)
Mourners posted signs and lit candles at Carson Elementary School in Puyallup, Wash. where Braden and Charles Powell attended school. The brothers were killed in an explosion caused by their father Josh Powell at his home on Feb. 5, 2012 -- days after a judge denied his request to regain custody of them.
A Pierce County fire investigator works his way through charred rubble, Monday, Feb. 6, 2012, at the home where Josh Powell and his two sons were killed Sunday, in Graham, Wash., in what police said appeared to be a deliberately set fire. Powell's wife Susan went mysteriously missing from their West Valley City, Utah, home in December 2009. (AP Photo/Ted S. Warren)
In this Aug. 19, 2011 photo, Josh Powell plays with his son Braden in a park near his home, in Puyallup, Wash. Powell had long been a person of interest in his wife. (Rick Egan | The Salt Lake Tribune Friday, August 19, 2011)
This photo from Facebook shows Susan Cox Powell in December of 2008.
A flier seeking information on the whereabouts of Susan Powell, who was reported missing Dec. 7, 2009, in Utah, is shown, Thursday, Dec. 17, 2009, at a press conference in Puyallup, Wash. Powell's family said Thursday they are saddened but not surprised that her husband Josh Powell has been named a person of interest in the investigation.
Josh Powell, the husband of Susan Powell, stands with supporters after a candle light vigil for his wife at the Church of Jesus Christ of Latter-day Saints in Puyallup, Wash., Sunday Dec. 20, 2009.
Judy Cox, the mother of Susan Powell, who was reported missing Dec. 7, 2009, in Utah, becomes emotional during a press conference, Thursday, Dec. 17, 2009, in Puyallup, Wash. Powell's family said Thursday they are saddened but not surprised that her husband Josh Powell has been named a person of interest in the investigation.
This undated photo provided by Chuck and Judy Cox shows Charlie Powell, who was killed along with his brother Braden by their father Josh Powell in a double-murder suicide. (AP Photo/Courtesy Chuck and Judy Cox)
In this undated photo provided by Chuck and Judy Cox, Judy Cox, right, sits at a table with her grandson Braden. (AP Photo/Courtesy Chuck and Judy Cox)
This undated photo provided by Chuck and Judy Cox shows Braden Powell. (AP Photo/Courtesy Chuck and Judy Cox)
In this undated photo provided by Chuck and Judy Cox, Chuck Cox sits with his grandsons, Charlie, left, and Braden, right, at the Coxes home in Pullayup, Wash. (AP Photo/Courtesy Chuck and Judy Cox)
In this undated photo provided by Chuck and Judy Cox, Chuck Cox plays with his grandsons, Charlie, right, and Braden, left. (AP Photo/Courtesy Chuck and Judy Cox)
ABC News obtained what it says was a voicemail Josh Powell left for his family members. In it, Powell said he couldn't live without the boys and didn't want to go on anymore.
In the recording played Tuesday on "Good Morning America," Powell also said he was calling to say goodbye and apologize.
"I'm sorry to everyone I've hurt," he is heard saying. "Goodbye."
An autopsy showed the children also suffered hatchet wounds to their necks.
As authorities work to determine exactly why Powell committed the murders at the Washington residence, investigators said they're no closer to answering the question they've had for two years.
"We still haven't identified or found where Susan Powell is," said West Valley, Utah, Police Chief Buzz Nielsen, who is in charge of the investigation into the young mother's disappearance.
The father of the 5- and 7-year-old boys painted himself as a tortured man, ridiculed without reason in the disappearance of his wife, steadfastly insisting he was innocent until the end.
Powell's horrific murder-suicide seemed to come out of nowhere. Just days before, in a motion seeking custody of his children filed with a Washington state court, Powell said he missed his wife, and would remain strong for the boys.
"A lesser person would fall under the intense scrutiny I am facing, but apparently my inherent resilience as a person makes it increasingly difficult for them to pursue their agendas," Powell wrote. "I am standing tall for my sons, but it deeply hurts to face such ridicule and abuse.
"I know my own heart is free of any guilt regardless of what people claim," he added.
Things changed dramatically when the judge ruled against him, ordering the children to remain with Susan Powell's parents for now.
On Sunday, Powell's boys came for a routine supervised visit. They ran ahead, the social worker falling behind. Powell then locked the door, used a hatchet on his kids, and lit the house on fire.
Ultimately, Powell and both boys died of smoke inhalation, Pierce County Medical Examiner's Office investigator Melissa Baker said Monday evening.
But they also suffered "chop injuries" that contributed to their deaths — 7-year-old Charles was struck on his neck and 5-year-old Braden had injuries to both his head and neck, Baker said.
Pierce County Sheriff's Detective Ed Troyer said investigators found a hatchet that they believe was used on the boys.
"We recovered a hatchet — a small ax," he said. "It was right there with" the bodies.
Authorities also said Powell had made thorough plans well ahead of the murders.
"This was definitely a deliberate, planned-out event," Troyer said.
He said minutes before the fire, Powell sent emails to several people saying, "I'm sorry. Goodbye." To others, including his cousins and pastor, he sent longer emails, with instructions on where to find his money and how to shut off his utilities. In at least one email, he wrote that he couldn't live without his boys, Troyer said.
But, he added, "There's no indication about Susan in anything that we've found so far."
Nielsen said detectives want to question Powell's father, Steve Powell, about Susan's disappearance. He described Steve Powell as another "person of interest" but noted the elder Powell is "not in our sights" in terms of any potentially imminent arrest.
Steve Powell has been in jail on voyeurism and child porn charges since last fall after authorities found explicit images on his computers during a search of his home in the case of his missing daughter-in-law.
After his arrest, the state turned the boys over to Susan Powell's parents, Charles and Judy Cox.
Steve Powell claimed on national television last year to have had a flirtatious or even sexual relationship with Susan — something her family has adamantly denied.
Josh Powell claimed that the night his wife vanished in December 2009, he took the boys from their West Valley City home, about 10 miles outside Salt Lake City, on a midnight camping trip in freezing temperatures — a story her parents never believed. Authorities searched the area in the central Utah desert but came up empty.
Less than a month after the disappearance, Josh Powell moved the boys to his father's home in Puyallup, south of Seattle.
Sunday's tragedy left the Coxes devastated. They spoke to reporters Monday to give a glimpse of the lives the boys led.
They said the boys played happily and didn't want to visit their father when the time came for their weekly Sunday visit. But Judy Cox said she talked them into going — and she now regrets it.
Charles Cox said he didn't necessarily think there was any more the court could have done legally to protect his grandchildren. However, he said he didn't like that there was only one supervisor during their visits with their father.
"We suspected that if he had the boys in his control, with him, and he felt the police were closing in, he was capable (of hurting them)," Cox said. "We didn't like that there was only one supervisor. Frankly, she couldn't have stopped him if he wanted to do something."
The boys were emotionally distant when they first arrived at their grandparents' home, Charles Cox said, but recently they had become warmer. And that gave the grandparents hope that maybe someday they would be able to relate what happened to their mother.
"They were like little robots. If you asked them about mommy, they would run away," he said. But "in the last week, I could not sit down without them climbing up on my lap."
Charles Cox said that the summer after his daughter disappeared, Braden drew a picture at day care of a van with three people in it, and told caregivers who asked him about it that it was a picture of his family going camping: "Mommy's in the trunk," the boy reportedly said.
But the boys had not recently made more comments to that effect, Charles Cox said, contradicting earlier remarks by his lawyer, Steve Downing, who told the AP that the older child had recently mentioned their mother being in the trunk.
Nielsen said Utah authorities would continue with their investigation, and hoped to make an arrest in the Susan Powell case this year.
"On a criminal case of this nature, you've got one shot. You've got to make sure everything is done right," Nielsen said. "Our case is not closed."